1. Field of the Invention
This invention pertains, in general, to a capacitive discharge ignition (“CDI”) system, and in particular but not by way of limitation, to a supplemental CDI system utilizing an energy storage device for initiation or re-initiation of combustion within internal combustion engines, thereby requiring minimal mechanical energy for initiation or re-initiation of combustion in an engine.
2. History of Related Art
Mechanical-start ignition systems for internal combustion engines are the bane to many users, regardless of the purpose of the engine. This is because the engines, which may be started by kick-starts, pull-starts, or other mechanical-based starting mechanisms, require a large amount of force to provide sufficient spark energy for ignition initiation. This problem becomes readily apparent during re-starting the engine, which may be very hot from prolonged system operation.
Such engines typically utilize magneto-based ignition systems. A magneto is an electric generator, which establishes a magnetic flux through the use of one or more permanent magnets. The magneto is a self-contained unit used advantageously for ignition where a generator and a battery are not needed to supply power to other accessories.
FIG. 1 is a typical magneto 100. The magneto 100 is housed in a magneto frame 110, and includes a left-hand magnet 115 and a right-hand magnet 120 connected thereto. A rotor 125 is also connected to the frame 110 and intermittently provides an electrical path between the left-hand magnet 115 and the right-hand magnet 120. A primary winding 130 of relatively few turns and a secondary winding 135 of a relatively large number of turns are wound over a laminated yoke 140.
The position of the rotor 125 shown in FIG. 1 provides a low reluctance path for the magnetic flux of the left-hand magnet 115 and a high reluctance path for the magnetic flux of the right-hand magnet 120, such that flux goes through the yoke 140 from left to right. When the rotor turns one-eighth of a revolution, it becomes horizontal, with each of the magnets 115, 120 acting in opposition relative to the yoke 140, thus resulting in zero magnetic flux. When the rotor 125 turns one-fourth of a revolution, or 90° from the position shown in FIG. 1, the rotor 125 now provides a low reluctance path for the right-hand magnet 120 and a high-reluctance path for the left-hand magnet 115. Thus the magnetic flux now goes through the yoke 140 from right to left. Each subsequent 90° interval results in the flux in the yoke 140 undergoing a complete reversal, which is generally recognized as an inductor type of A/C generator.
Referring now to FIG. 2, a schematic view of a magneto-ignition system 200 incorporating the magneto 100 of FIG. 1 is shown. A simplified exemplary CDI device 205 is generally described herein and below.
One end of both the primary winding 130 and of the secondary winding 135 is grounded (FIG. 1). The other end of the magneto 100 is connected to a trigger coil 210. This contact to ground is actuated by the trigger coil 210, having solid state electronics, but having the timed release controlled by the CDI 205. A switch is provided to ground and thus short-circuit the secondary winding 135 when it is desired to stop the system 200. A capacitor is connected to the trigger coil 210 and ground to absorb the energy of the spark that occurs when the CDI 205 connects with ground.
Referring to FIGS. 1 and 2 in combination, when the CDI 205 completes the circuit, the primary winding 130 is short-circuited, and the varying flux in the magneto 100 produced by the rotation of the rotor 125 induces an alternating current in the secondary winding 135, which in turn produces an alternating flux in the magneto 100. With the rotation of the rotor 125, the current in the secondary winding 135 rises cyclically to maximum values, and at these instants the CDI causes the circuit to open suddenly, interrupting the current in the primary winding 130 and thus causing a sudden collapse of the flux in the magneto 100. This induces a high-impulse EMF in the secondary winding 125 that is transmitted to the CDI and thence to a proper spark plug(s) 220.
Because the magneto 100 requires some sort of mechanical input to initiate rotation of the rotor 125 therein, on starting, the speed of the magneto 100 may be so low that the EMF is not sufficient to produce a hot spark and/or multiple sparks, and thus initiate combustion in an engine. During re-start of the engine, similar problems occur, such as spark plug fouling, improper engine cylinder thermal properties (i.e. too hot or too cold), improper fuel/air ratio, and similar problems.
In mechanically-timed ignitions, one method of overcoming such problems is by impulse starting, in which a rotor of a magneto is driven through a spring. During cranking the rotor is restrained from turning until the engine moves to the proper firing position, at which time the rotor is suddenly released. The energy stored in the spring produces a high, instantaneous, angular velocity to the rotor, resulting in a high EMF and a hot spark.
Such impulse starters are commonly used in older aircraft applications. However, as can be appreciated by the user of the engine, supplying enough mechanical energy during cranking can be tedious, time-consuming, and wearing. For example, in the motorcycle racing industry, re-starting a hot engine by multiple kick-starts can result in loss of precious amounts of time. Similar frustration is found by the avid (or not-so-avid) lawn care consumer, who must exert large amounts of physical energy while pulling the crank to start or re-start the engine.
In the motorcycle industry in particular, typical motorcycle engine ignition has low spark energy at the lower RPM where starting occurs. Several methods have been used to provide more energy to the spark plugs, and will be described briefly below.
First, spark plugs have been provided with small diameter center electrodes. These have shown to reduce the voltage necessary to ionize the spark plug gap and thus quickly bring the engine to steady-state performance. Such an approach has been shown to assist poor engine performance when fuel/air ratios are too lean (during a cold engine start up) or too rich (during a hot engine start up).
Second, motorcycles have been fitted with automatic and manual compression releases. These releases allow the engine to be kick-started easier through the release of compression in the cylinders, thus increasing the speed of rotation of the rotor, increasing the corresponding spark energy from the magneto.
Third, timing on the ignition systems has been adjusted to optimize the ignition of the fuel/air mixture. These complex systems require precise adjustments to obtain the most efficient mixture of fuel/air in the engine, and assist in minimizing the possibility of kickback, which is the firing of the engine in reverse. The reversal of the engine often causes injury to the rider and mechanical failure in the starting engine.
A choke lever may also be used to enrich the fuel/air mixture in the carburetor. Such an approach is especially useful in cold start situations due to the increased density of the cold air at engine start-up. A hot start lever may likewise be provided to lean out the fuel/air mixture in the carburetor, which also is useful when the engine stalls and an accelerator pump or the like is errantly activated in an attempt to prevent engine stall.
Probably the most obvious approach to solve the start/re-start problems in this industry would be installation of an electric starting motor, such as those used in automotive applications. An electric starting motor would spin the engine fast enough and with multiple revolutions to overcome the low spark energy at start up while allowing the engine to reach ideal fuel/air mixture.
Unfortunately, these systems have proven to be less-than-ideal, and as a result are not widely accepted. In particular, each of these systems adds increased weight, which is undesirable, especially in motorcycle racing, lawn mowing, landscaping and similar applications. Further, addition of such components may alter the weight distribution and balance of the mechanism, which is unacceptable in certain applications. Each system further adds significantly increased cost and complexity, and results in unsolvable breakdowns that require professional assistance to repair. Such components may also add increased rotational mass (particularly in the example of the electric starting motor), which is especially noticeable in racing applications where engine acceleration is critical. Finally, each component may be subject to dirt and water contamination, which will foul the starting and charging system of the application, and require significant time to repair.
As a result, all of these solutions go virtually unused in the magneto-based ignition industry, or if they are used, the user deals with the undesired compromise. The current magneto-ignition engines start poorly even in ideal situations, or not at all in less than ideal situations. And most of the current magneto-ignition engines require more tune-ups and repairs than should be necessary. Overall, these engine-starting problems cause far more frustration that need be, at a cost much higher than it should be.
These problems only get worse. Current and pending legislation in the United States mandates the use of four-stroke motorcycle engines, which have notoriously poor starting performance due to environmental concerns. These same concerns affect every industry utilizing magneto-ignition systems, and are forcing many manufacturers to adapt to four-stroke engines.
Add to these problems the harmful environmental effects such existing magneto-based ignition engines create. In particular, the multiple starts and re-starts of these engines release harmful hydrocarbons and other byproducts of fuel that does not combust within the engine. With recent and projected restrictions on the release of harmful environmental products both in U.S. and abroad, these problems will only become more apparent.